A suicide bomber set off a device in southeastern Iran, killing at least 40 people including several high-ranking Revolutionary Guards officers.
The officials were reportedly meeting with tribal leaders in Sistan-Baluchistan province Sunday when they were attacked.
Iranian leaders at first blamed the United States and the United Kingdom for supporting the bomber -- allegations that were denied -- but Monday said Pakistan was to blame -- an allegation Pakistan denied.
Iran similarly blamed outside forces for violent protests following the disputed election last summer in which President Mahmoud Ahmadinejad was given a second term in office.
There were reports a local group that claims to fight in support of Sunni Muslims carried out the attack.
Six Revolutionary Guards commanders were among the 42 people killed, official Iranian reports said. Dozens of other people were injured. The attack occurred as a meeting between local tribal leaders and the Revolutionary Guards was beginning.
China marked the 60th anniversary of the assumption of power by the Communist Party with a huge parade that show cased its military might.
The ceremonies centered on Tiananmen Square where, on Oct. 1, 1949, Mao Zedong declared the establishment of the People's Republic of China.
The parade with an estimated 100,000 participants showed off military hardware and serves as a reminder the world's most populous country -- 1.3 billion -- can field an important army in the traditional sense of military power.
But China's true strength wasn't seen on the parade grounds. Instead, it is inked in ledger books where the figures show Beijing holds considerable international sway economically. The United States is particularly vulnerable along this line as China in recent years has amassed more than $1 trillion in U.S. dollars in its foreign reserves (and another $1 trillion in other currencies).
It was the third series of missile tests by Tehran, which had a secret nuclear facility unveiled last week and has talks with the permanent members of the U.N. Security Council and Germany this week about its nuclear program.
Iran says its nuclear program is for peaceful purposes but many Western countries fear it may be a precursor to Tehran developing a nuclear weapon.
The Iranian leadership, particularly President Mahmoud Ahmadinejad, has been openly hostile to Israel.
Tests over the past few days included Monday's firing of the Shahab-3 rocket, which is believed to have a range of 1,240 miles. Two classes of missiles with less range were fired Sunday.
Even before the Monday tests, U.S. officials said they had the international support to impose "severe additional sanctions" on Tehran. However, Security Council members Russia and China have been successful in the past in keeping tough penalties from being levied. It is unknown if the revelation of a secret nuclear facility would change that stance.